Aerogel made from watermelon is light enough to rest upon a dandelion.

Credit: ACS Nano

Aerogel made from watermelon is light enough to rest upon a dandelion.

Credit: ACS Nano

Heating a juicy watermelon in an autoclave at 180 °C for 12 hours will not improve the flavor of this summertime treat. In fact, it transforms the material into something that’s black and inedible. But the burnt melon also happens to be a hydrogel—a spongelike material that could find use as an adsorbent, a catalyst support, an electrode material for batteries, or even a supercapacitor. Freeze-drying that watermelon-derived hydrogel produces an aerogel, a lightweight material that also has promising properties for catalysis and in electronic applications. The simple, environmentally friendly hydrogel and aerogel syntheses were discovered by An-Wu Xu of the University of Science & Technology of China, Xiangke Wang of the Chinese Academy of Sciences, and coworkers (ACS Nano, DOI: 10.1021/nn400566d). Furthering the fruits of their labor, the researchers also laced the aerogels with Fe3O4 nanoparticles, creating a magnetite-carbon aerogel. They demonstrated that this composite aerogel could be a promising material for storing energy.